1. Field of the Invention
Implementations of various technologies described herein generally relate to the field of seismic data processing, and more specifically, to prestack depth migration.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Seismic surveying may be used to determine structures or compositions of subsurface earth formations. For example, seismic surveying may be used to determine the presence of useful materials, such as petroleum, in the subsurface earth formations. Generally, the process of seismic surveying includes deploying an array of seismic sensors at or near the earth's surface at selected geographic positions and deploying one or more seismic energy sources at selected locations, also at or near the earth's surface. The one or more seismic energy sources may be actuated, causing seismic energy to emanate from the sources, traveling generally downwardly through the earth's subsurface until it reaches one or more acoustic impedance boundaries in the earth. The seismic energy may be reflected from the one or more impedance boundaries, where it may then travel upwardly until detected by one or more of the seismic sensors. Structures and compositions of the earth's subsurface may be inferred from the travel time of the reflected seismic energy, from the geographic position of the source to each of the sensors, and from the amplitude and phase of the various frequency components of the reflected seismic energy with respect to the energy emanating from the seismic source.
Structures of the earth's subsurface may be inferred from the travel time of the seismic energy from the source to the acoustic impedance boundaries and back to the seismic sensors at the surface. In order to infer depth of and the structures of subsurface earth formations from reflection seismic travel times measured at the earth's surface, it may be necessary to determine the acoustic velocity of the various formations through which the seismic energy passes. Velocities of the earth formations may vary both with respect to depth in the earth (vertically), and with respect to geographic position (laterally). Seismic data, however, are typically recorded only with respect to time. Methods known in the art for estimating velocities of the earth formations both vertically and laterally rely on inferences about the travel path geometry of the seismic energy as it travels from the seismic source to the various seismic receivers deployed at or near the earth's surface.